Field of the Invention
The present invention relates to an image forming apparatus, a control method thereof, a printing system, and a non-transitory computer-readable medium and, more particularly, to control when a post-processing apparatus configured to perform crease processing is connected to an image forming apparatus.
Description of the Related Art
On the printing market, various output materials are created using post-processing apparatuses for sheets having undergone image formation by an image forming apparatus. For example, there is a saddle stitching machine aiming to create (saddle-stitch) a simple booklet by folding an output sheet bundle into two at the center and stapling the fold. There is also a sheet folding apparatus aiming to divide an output sheet into three panels, fold one panel inside, and fold (C-fold) one panel on the opposite side to overlap that panel so as to be able to easily insert the sheet into an envelope or the like.
When the above-mentioned folding is executed, a force that stretches an outer sheet against the folding direction acts to crack the crease (to be referred to as a crack of the spine hereinafter), and the spine is visible as a white color. If this portion has a pattern (for example, an image) or a character, the appearance is greatly degraded. To prevent this, a crease processing for making a crease at a fold in advance is known so as to easily fold an outer sheet and not to generate a crack in the spine. A post-processing apparatus that performs crease processing is an apparatus called a creaser.
Types of folding methods can be classified into “mountain fold” and “valley fold” in accordance with a direction in which a sheet is folded after crease processing. The mountain fold is a method of folding, into a mountain shape, a surface against which the creasing blade of a creasing mechanism is pressed. The valley fold is a method of folding, into a valley shape, a surface against which the creasing blade is pressed. Although both the mountain fold and valley fold are effective for preventing a crack of the spine, and either fold method is usable, the mountain fold is generally used. The valley fold is used when it is superior to the mountain fold in terms of the type of sheet to be used, the folding position, the appearance, and the like. There has already been known an image forming system that automatically switches between the mountain fold and the valley fold by using sheet information and bookbinding information.
For example, in Japanese Patent Laid-Open No. 2012-41187, the settings (for example, monochrome, bookbinding designation, bookbinding cover, and medium information) of an output material are obtained from sheet information and bookbinding information, either of the mountain fold and valley fold is decided, and crease processing is executed on a necessary surface. When an image is printed at the crease portion and a crack of the spine is readily generated, crease processing is performed to make a mountain fold. When a crack of the spine is hardly generated, crease processing is performed to make a valley fold.
However, in Japanese Patent Laid-Open No. 2012-41187, when crease processing is performed a plurality of times (at a plurality of portions) on one sheet in order to execute crease processing on a necessary surface in accordance with settings (for example, Z-folding, C-folding, or bookbinding cover), execution of crease processing on two, front and back surfaces is not considered. In the case of such designation, a post-processing apparatus capable of simultaneously executing crease processing on the front and back surfaces can execute crease processing at once by one feeding operation. However, a post-processing apparatus capable of executing crease processing on only either the front or back surface by one feeding operation needs to perform feeding twice to the creasing apparatus for one sheet for which crease processing is set for the two, front and back surfaces. If feeding is performed twice, the procedures and time until a desired printed material is obtained are increased. Since the feeding work is performed a plurality of times, the load on a sheet is also increased, putting an excessive load on the output material.